Fuel injection systems for internal combustion engines



Se t. 13, 1966 M. H. WESTBROOK ETAL 3, 8

FUEL INJECTION SYSTEMS FOR INTERNAL CQMBUSTION ENGINES Filed Sept. 8, 1964 2 Sheets-Sheet 1 THROTTLE 2 P504 L l4 ACCELERATION 4ND IDZE [4a TRANSDUCER COLD START TRANSDUCER INIEC r012 13 MA N/ FOLD PRE55URE TRA NSDUCER COMPUTER TR/GGE DISTRIBUTOR Inventors M. h. Wes?! brook R. T Skip war-M B A EM M. H. WESTBROOK ETAL 3,272,187

Sept. 13, 1966 FUEL INJECTION SYSTEMS FOR INTERNAL COMBUSTION ENGINES Filed Sept. 8, 1964 2 Sheets-Sheet 2 Fig.2

7 lnvemors A1. h. Westbro A. K's/m wer:-

By I .Mrneys United States Patent 3,272,187 FUEL INJECTIQN YSTEMS FUR INTERNAL COMBUSTION ENGlNES Michael Hereward Westbrook and Richard Teft Skip- Worth, both of Leamington Spa, England, assignors to Associated Engineering Limited, Learnington Spa, England, a British company Filed Sept. 8, 1964, Ser. No. 394,824 Claims priority, application Great Britain, Sept. 9, 1963, 35,495/ 63 7 Claims. (Cl. 123-32) The present invention relates to fuel injection systems for internal combustion engines and more particularly to improvements in the fuel injection system described in copending application No. 284,031 filed March 29, 1963.

According to the system described in the aforementioned application, a fuel injection system for internal com-bustion engines comprises at least one electromagnetically operated fuel injection valve, a control circuit producing electrical pulses for energizing said at least one injection valve, so that the valve or a valve is open for a period depending on the duration of each of the pulses to pass fuel to the engine, and a computer device fed with a plurality of signals which respectively vary with variations in parameters atfecting or affected by the engine operation and controlling the duration of the pulses produced by the control circuit. As described, the control circuit comprises a monostable m-ulti-vibrat-or for producing the electrical pulses and the duration of the pulses is varied by varying two control voltages applied to the multi-vibrator circuit. One of these control voltages is derived from the output of the computer device and the other voltage varies as a function of the speed of rotation of the engine, and the voltages are applied to two different points on the multivibrator circuit.

According to one feature of the present invention the computer is arranged to produce two control voltages one being variable in accordance with changes in the manifold pressure of the engine and the second varying with changes in other parameters affecting or aifected by engine operation, such as water temperature and engine idling speed and acceleration.

According to a further feature of the invention, the control circuit is arranged so that its output pulse length varies linearly with respect to the control voltage produced in dependence upon manifold pressure and is proportional to the other control voltage produced from the computer device.

The system may also include a discriminator for producing a further control voltage proportional to engine speed, which is also fed to the pulse generator so that the pulse length varies as a function of engine speed.

The invention will now be further described by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a block diagram of one embodiment of fuel injection system according to this invention.

FIGURE 2 is a circuit diagram of one embodiment of the control pulse generator and,

FIGURE 3 is a circuit diagram of one embodiment of the computer circuit.

Referring to FIGURE 1, the fuel injection system illustrated is intended for a four cylinder internal combustion engine and comprises a fuel tank 1 from which fuel is pumped under pressure by the pump 2, through a filter 3 to a common rail 5 supplying fuel at constant pressure to four individual electromagnetically operated fuel injection valves, shown at 41-. These valves may be constructed as described in our copending application No. 327,188 or 362,385.

A separate injection valve is provided for each cylinder,

ice

either mounted in the inlet manifold of the engine or in the case of direct injection using higher pressures, in the cylinder head or cylinder. A return pipe 6 from the common rail 5 by-passes fuel back to the tank 1 through a control valve 7 which determines the actual pressure in the rail 5.

Since the injection valves 4 are supplied with fuel at constant pressure, a periodic activation of an injection valve for a time duration dependent upon engine operating conditions will meter the fuel supplied to the engine through each injection valve. Each valve is energised by a current pulse of predetermined duration, which pulse is derived from the control pulse generator 8 and allocated by the distributor 9 according to the firing sequence of the engine. A quantity of fuel proportional to the electrical pulse duration is delivered in an atomised form into the cylinder through the open inlet valve, or directly into the combustion chamber, in the case of the high pressure ap plication, at a predetermined point in the engine cycle.

The duration of the pulses fed to the valves via the distributor is controlled by the control pulse generator 8, which in turn is controlled by two voltages V1 and V2 from the computer 10. The control pulse generator is triggered from a trigger contact assembly 11 mounted in the distributor housing and operating at the firing frequency of the engine. The distributor and trigger contact assembly may be constructed as described in our copending application No. 362,384.

The computer 10 is fed with information supplied by a number of transducers 12, 13 and 14 each responsive to one or more conditions of engine operation. In this embodiment the individual transducers are arranged to sense the following conditions of engine operation:

Transducer 12-Manifold pressure Transducer 13Engine water jacket temperature (cold start and warm up) Transducer 14-Acceleration and idling transducer.

In operation, the driver primarily controls a valve, located in the induction manifold from a conventional throttle pedal 15 which in turn influences the behaviour of the transient transducers in response to the engine Operation, and hence the fuel quantity is computed by the system to satisfy the required operating condition.

The manifold absolute pressure transducer 12 comprises a resistance winding 12a and wiper 12b contained within a casing 12c sealed by a diaphragm 1 2d responsive to manifold pressure and containing a quantity of gas so that movement of the diaphragm and thus the position of the Wiper is influenced by ambient temperature as well as manifold absolute pressure.

The cold start transducer 13 for fuel enrichment during the engine warm up period comprises a thermistor connected into the computer circuit. The arrangement is such that when the engine starter is operated, the degree of enrichment is increased for so long as the starter is engaged.

The acceleration and idling transducer 14 provides fuel enrichment on acceleration by means of a potentiometer 14b whose wiper 14a is mechanically coupled to the throttle pedal 15 and electrically connected to the computer circuit. The transducer 14 also includes contacts which are closed under engine idling conditions.

The manner in which the transducers 12, 13 and 14 are connected to and operate with the computer circuit will be more fully described later with reference to FIGURE 3.

The control pulse generator may further be controlled by an output voltage from a discriminator, shown in broken lines at 16 which produces a voltage proportional to engine speed. The discriminator may be fed with trigger pulses from the contact breaker 11 which have a repetition rate varying as a function of engine speed. This discriminator may be an electronic arrangement as described in our copending application No. 284,031 or a mechanical arrangement as described in our copending application No. 425,509, filed January 14, 1965. Where a discriminator is included in the system, the duration of the output pulses from the control pulse generator will vary as a function of engine speed and this variation can be made to follow a pre-determined characteristic suitable to a particular engine design.

Although the inclusion of a disciminator in the system may be advantageous for use with some engines, its use is not essential with all engines.

Other methods of triggering the control pulse generator, instead of by means of the contact breaker 11, may be employed.

Such methods are:

(a) Electromagnetic In this system a coil Wound on a permanent magnet or an electromagnet generates a voltage when a second ferrous object forming an armature is moved rapidly across one end of the magnet used. By shaping both the pole piece of the magnet and the moving ferrous armature to present the minimum edge length in the direction of motion a sharp pulse can be obtained. The pulse amplitude does however increase directly with speed and suitable account of this must be taken in the circuitry used for generating the control pulses for the fuel injection system.

It is possible using this means to provide a non-contact triggering system from either the distributor or the flywheel of the engine by the use of a suitable number of armature pieces or projections according to the type of engine with which the system is being used.

It is also possible to make the armature pieces permanently magnetic instead of the core of the coil, the operating principle being the same.

(b) Photoelectric In this system a lamp and photocell arrangement is used. The light from the lamp falling on the photocell is interrupted by either a series of reflecting and nonreflecting strips, or by slits on a disc attached either to the engine flywheel or to the distributor. This system has the advantage that the output does not vary with speed.

(c) Inductive and capacitive It is also possible to use inductive or capacitive triggering, employing a high frequency energising signal of about ten times the fastest trigger rise frequency, to energise a capacitive or inductive device. A moving armature driven by the engine and influencing the capacitive or inductive device causes a change of amplitude in the high frequency signal appearing across the device when the device is suitably loaded and this change in amplitude is used to produce the triggering pulses.

FIGURE 2 is the circuit diagram of one embodiment of the control pulse generator shown at 8 in FIGURE 1.

The pulses are generated by a monostable multivibrator circuit comprising transistors TR1 and TR2 and including the timing capacitor C1 which is charged through the constant current transistor TR4. In the steady state or rest condition of the circuit, transistor TR2 is held in the normally ON condition, its base current being supplied by the collector current of the NPN transistor TR4. Transistor TR1 is normally held OFF by a small negative bias supplied through terminal T3 from the computer circuit. When a negative going triggering pulse derived from the trigger contacts 11 is applied via terminal T2 and diode D2 to the base of transistor TR1, this transistor is turned ON and a voltage equal to the voltage swing at the collector of TR1 is developed across capacitor C1. This voltage immediately turns transistor TR2 OFF. The signal from the collector of TR2 is fed via resistor R1 to the base of TR1 to hold this transistor in the ON condition. This state of the multi-vibrator circuit will be maintained until capacitor C1 has charged through transistor TR4 to a voltage which is sufficient to turn transistor TR2 ON again. The multi-vibrator then reverts to its original state. The time 1 taken for this operation is given by:

where C is the capacity of capacitor C1 i is the collector current of transistor TR4 V is the voltage change across capacitor C1 For this duration of time t, the voltage at the collector of transistor TR2 is, say -12 v. whereas during the steady state of the circuit the collector voltage of TR2 is, say 2 v. A negative going pulse of pulse length t and amplitude 10V is therefore produced at the collector of transistor TR2. Transistor TR3 provides a low impedance discharge path for capacitor C1 when transistor TR2 is turning ON.

The pulse length t can be varied by two parameters, namely the voltage change across capacitor C1 and the charging current through transistor TR4. The control of the voltage change is achieved by feeding a voltage V1 from the computer 10 and derived from the manifold pressure transducer 12 to terminal T1 and hence via diode D1 to the collector of transistor TR1. The charging curent through transistor TR4 is varied by varying the potential at the base of this transistor which is fed, via terminal T4, with a voltage V2 from the computer which varies in dependence upon variations of the output from the cold start transducer 13 and the acceleration transducer 14.

The pulse length t is thus varied by the two control voltages V1 and V2 from the computer circuit; the pulse length varying linearly with voltage V1 and proportional to voltage V2.

The negative-going pulse at the collector of TR2 is D.C. restored to earth by capacitor C2, diode D3 and resistor R2, and is then fed through the emitter follower amplifier stages TR5 and TR6 to the output stages TR7 and TR8. The output transistor TR8 is turned OFF during the steady state condition of the circuit. A small negative bias developed across resistors R3 and R4 in parallel is applied to the emitter of this transistor to make certain that is held OFF even at elevated temperatures. When the input to the base of TR8 goes negative due to a pulse, TR8 is turned ON and the energising solenoid of the or each fuel injection valve then connected to the current via terminal T5 and the distributor 9 is connected in series with the supply through bias resistors. When transistor TR8 is turned off, an E.M.F. is generated by the or each injector. This generated E.M.F. is limited to a safe value by resistor R5 connected across the injector.

The bias resistors mentioned above are preferably mounted remote from the pulse generator as there is a considerable amount of heat generated in the resistors and heating of the pulse generator is to be avoided. The power output transistors TR7 and TR8 are mounted on a heat sink.

The computer circuit is shown in FIGURE 3. This circuit is designed to process the signals from the various transducers 12, 13 and 14 and to put them into a suitable form of feeding to the pulse generator 8. The circuit receives signals which are functions of the following: manifold pressure, (transducer 12), water temperature (transducer 13), and acceleration (transducer 14). The circuit may be arranged to provide the supplies for the transducers as well as for the trigger contacts.

The circuit comprises a potential divider P including variable resistors RV1 and RV2 which provide two voltages for the manifold pressure transducer 12. The high pressure end of the resistance track 12a of this transducer can be supplied with a voltage which can be varied between, say 0.9Vs and 0.54Vs, whilst the low pressure end of the resistance track of the transducer can be supplied With a voltage which can be varied between, say 0.1Vs and 0.36Vs, where Vs is the supply voltage. The voltage derived from the slider 12b of transducer 12 is fed via the NPN emitter follower stage TR9 to the output terminal T8, from whence it is fed as the control voltage V1 to the terminal T1 of the control pulse generator.

The same potential divider produces a 0.1Vs potential which is fed from terminal T9 to terminal T3 of the control pulse generator to provide the emitter bias to transistor TR1, The purpose of resistor R and capacitor C10 is to degenerate the signal to such an extent as to eliminate the possibility of the pulse generator being triggered by abrupt changes of the signal.

The automatic increase in pulse length required when the engine water is cold is obtained by means of the thermistor 13, as follows. The control voltage input V2 to the pulse generator is at a potential which is partly determined by resistors R11 and R12 when diode D10 is not conducting. The voltage at the junction of these resistors is fed via the emitter following transistor TRIO to the terminal T7 which is connected to terminal T4 of the control pulse generator. When D10 does conduct the potential at the junction of R11 and R12 is modified and the pulse length is increased. The resistors which determine, when diode Dill will conduct and what the characteristic will be, are R13, R14 and R15 in combination with the thermistor 13. The values of R13, R14 and R15 can only be accurately determined after some practical tests with a particular type of engine installation. The function of resistor R16 is to raise, ie to make more negative, the potential on the cathode of D111 when the engine starter button is pressed. To this end, terminal T6 is connected directly to the starter motor. The increase in pulse length produced when the starter button is pressed is thus a function of the water temperature.

The acceleration transducer 14 is intended to produce a voltage signal which is proportional to throttle angle and the wiper 14a of the potentiometer 14b is mechanically coupled to the throttle pedal. This signal is differentiated by C11 and R17 to produce a signal which is proportional to the rate of change of throttle angle. This signal is fed through transistor TR11 and added to the signal produced at the junction of resistors R11 and R12. The resultant signal at this point is fed via the emitter follower TR10 and terminals T7 and T4 as the V2 voltage to the pulse generator. Again practical experiment is necessary accurately to determine the time constant C11, R17 and the value of resistor R18 for a particular engine installation.

Switch S1 is an idling control and closes when the throttle is closed. When the switch is closed, resistor R19 is connected in parallel with R1, thus raising the potential at the junction of resistors R11 and R12 and modifying the control voltage V2 fed to the pulse generator to provide slight fuel enrichment when the throttle is closed. The optimum value of resistor R19 for any engine is again determined by practical experiment.

Whilst a particular embodiment has been described it will be understood that various modifications may be made without departing from the scope of this invention.

Thus the computer may handle additional parameters to those described. Also, obviously, the system may be employed with engines having other numbers of cylinders than four, as specifically described.

We claim:

1. A fuel injection system for internal combustion engines comprising at least one electromagnetically operated fuel injection valve, a control circuit producing electrical pulses for energizing said at least one injection valve, so

that said valve is opened for a period depending on the duration of each of the pulses to pass fuel to the engine, said control circuit comprising a monostable multivibrator having a timing circuit consisting only of components having values which are invariable during the operation of the system and including a timing capacitor which is charged through a constant current device, means for feeding said timing circuit with first and second variable voltages which vary as a function of parameters of engine operation to control the duration of the output pulses fed to energize said at least one injection valve and wherein said variable voltages fed to the timing circuit are derived from a computer device, independent of the control circuit and comprising a plurality of variable resistance devices connected across a voltage supply, and means for respectively varying said resistance devices in response to different parameters of engine operation, and wherein the duration of the output pulses varies linearly with respect to the first control voltage produced in dependence upon manifold pressure and is proportional to the second control voltage produced in response to other parameters of engine operation.

2. A fuel injection system for internal combustion engines comprising at least one electromagnetically operated fuel injection valve, a control circuit producing electrical pulses for energizing said at least one injection valve, so that said valve is opened for a period depending on the duration of each of the pulses to pass fuel to the engine, said control circuit comprising a monostable multivibrator having a timing circuit consisting only of components having values which are invariable during the operation of the system and including a timing capacitor which is charged through a constant current device, means for feeding triggering pulses to the multivibrator to cause it to change its state and produce an output pulse of a duration depending upon the charging time of the capacitor, means for applying a first voltage to the capacitor to vary its charging time, means for applying a second voltage to control the constant current device and hence also vary the charging time of the capacitor and thereby the duration of the output pulses fedto energize said at least one injection valve, and a computer device independent of the control circuit and comprising a plurality of variable resistance devices connected across a voltage supply, and respectively producing said first and second voltages in response to manifold pressure and at least one other parameter of engine operation, so that the duration of the output pulses varies linearly with respect to the first voltage produced in dependence upon manifold pressure and in proportional to the second voltage produced in response to at least one other parameter of engine operation.

3. A fuel injection system for internal combustion engines comprising at least one electromagnetically operated fuel injection valve, a control circuit producing electrical pulses for energizing said at least one injection valve, so that said valve is opened for a period depending on the duration of each of the pulses to pass fuel to the engine, said control circuit comprising a monostable multivibrator having a timing circuit consisting only of components having values which are invariable during the operation of the system and including a timing capacitor which is charged through a constant current device, means for feeding triggering pulses to the multivibrator to cause it to change its state and produce an output pulse of a duration depending upon the charging time of the capacitor, means for applying a first voltage proportional to manifold pressure to the capacitor to vary its charging time, means for applying a second voltage which is proportional to at least one other parameter of engine operation to control the constant current device and hence also vary the charging time of the capacitor and thereby the duration of the output pulses fed to energize said at least one injection valve, and a computer device comprising a plurality of variable resistance devices connected across a voltage supply, and respectively producing said first and second voltages in response to manifold pressure and said at least one another parameter of engine operation.

4. A system as claimed in claim 3 in which the computer comprises a voltage supply, a manifold pressure transducer including a variable resistance element connected across said voltage supply, a transistor emitter follower stage fed with the output from said variable resistance and feeding said first voltage to said charging capacitor, further transducers comprising variable resistance devices which vary in response to other parameters of engine operation connected across said voltage supply, a resistor network combining the output voltages from said further transducers and a further transistor emitter follower stage fed from said resistor network and feeding said second voltage to control said constant current device.

5. A system as claimed in claim 4, in which one of said further transducers is a thermistor responsive to engine water temperature and a diode is connected between said transducer and a point on said resistor network, and means including said thermistor for biasing said diode so that its conductance and hence the output from the Water temperature transducer applied to said resistor network varies so as to increase the duration of the output pulses when the engine water is cold.

6. A system as claimed in claim 4, in which one of said further transducers produces an output which is proportional to engine acceleration and comprises a potentiometer whose movable contact is mechanically coupled to the throttle pedal of the engine.

7. A system as claimed in claim 3, including a discriminator for producing a further control voltage proportional to engine speed, and means for feeding said further control voltage to the control circuit so that the duration of the output pulses also varies as a function of engine speed.

References Cited by the Examiner UNITED STATES PATENTS 2,910,054 10/1959 Schutte 12332 2,918,911 12/1959 Guiot 12332 2,927,567 3/1960 Breeding 123-32 3,032,025 5/1962 Long et al. 12332 MARK NEWMAN, Primary Examiner.

RICHARD B. WILKINSON, Examiner. 

1. A FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINES COMPRISING AT LEAST ONE ELECTROMAGNETICALLY OPERATED FUEL INJECTION VALVE, A CONTROL CIRCUIT PRODUCING ELECTRICAL PULSES FOR ENERGIZING SAID AT LEAST ONE INJECTION VALVE, SO THAT SAID VALVE IS OPENED FOR A PERIOD DEPENDING ON THE DURATION OF EACH OF THE PULSE TO PASS FUEL TO THE ENGINE, SAID CONTROL CIRCUIT COMPRISING A MONOSTABLE MULTIVIBRATOR HAVING A TIMING CIRCUIT CONSISTING ONLY OF COMPONENTS HAVING VALUES WHICH ARE INVARIABLE DURING THE OPERATION OF THE SYSTEM AND INCLUDING A TIMING CAPACITOR WHICH IS CHARGED THROUGH A CONSTANT CURRENT DEVICE, MEANS FOR FEEDING SAID TIMING CIRCUIT WITH FIRST AND SECOND VARIABLE VOLTAGES WHICH VARY AS A FUNCTION OF PARAMETERS OF ENGINE OPERATION TO CONTROL THE DURATION OF THE OUTPUT PULSES FED TO ENERGIZE SAID AT LEAST ONE INJECTION VALVE AND WHEREIN SAID VARIABLE VOLTAGES FED TO THE TIMING CIRCUIT ARE DERIVED FROM A COMPUTER DEVICE, INDEPENDENT OF THE CONTROL CIRCUIT AND COMPRISING A PLURALITY OF VARIABLE RESISTANCE DEVICES CONNECTED ACROSS A VOLTAGE SUPPLY, AND MEANS FOR RESPECTIVELY VARYING SAID RESISTANCE DEVICES IN RESPONSE TO DIFFERENT PARAMETERS OF ENGINE OPERATION, AND WHEREIN THE DURATION OF THE OUTPUT PULSES VARIES LINEARLY WITH RESPECT TO THE FIRST CONTROL VOLTAGE PRODUCED IN DEPENDENCE UPON MANIFOLD PRESSURE AND IS PROPORTIONAL TO THE SECOND CONTROL VOLTAGE PRODUCED IN RESPONSE TO OTHER PARAMETERS OF ENGINE OPERATION. 